Download Moles! - Ms. Johnson Teaches Science!

Moles!
S
What is a mole?
It is a unit of measure!
S The mole is used in chemistry to express very large
quantities of atoms or molecules
S One mole is equal to 6.02 x 1023 atoms/molecules/things!
S So what does a chemistry mole look like?
Moles in Chemistry
S One mole of water is only 18 g in mass
S 1 mole of donuts would cover the Earth completely, and be
8 m deep!
S 1 mole of pennies would be enough for the whole world to
spend 1 million dollars each day!
Where did the mole come from?
S The standard number used for the mole, 6.02x1023 was
chosen because that is the number of particles found
experimentally in 12g of carbon-12
S Why carbon-12? It was arbitrarily chosen as the reference point
for the International System of Units
S 6.02x1023 is also called Avogadro’s number in honor of
Italian physicist Amedeo Avogadro
S He had proposed that equal volumes of gas contained equal
numbers of particles
So, why do we care???
S The mole helps us understand what is happening during a
chemical reaction at a macroscopic scale
S We can find out exactly how much of a substance is needed
for a chemical reaction to occur. This helps us prevent
wasting any expensive chemicals and ensuring that we get
exactly what we want out of a reaction.
Ms. Johnson, we are so excited
about the mole! Let’s get
started!
Step 1: Molar Mass
S Molar mass is a physical property of a substance
S It is the weight of one mole of some substance
S Expressed in unit form as g/mol
S So we have the mass (g) divided by the amount of the
substance (1 mole)
S Shortcut time: the molar mass of an element is it’s atomic
mass!
Solving for the Molar Mass of
an Element
S The molar mass of Oxygen is:
S The molar mass of Magnesium is:
S The molar mass of Tellurium is:
Solving for the Molar Mass of a
Compound
1.
Determine the elements you have in the compound
2.
Find the atomic mass of those elements
3.
Determine how many of each element you have
4.
Multiply the number of elements you have by the atomic
mass of that element
5.
Add it all together!
Example
Let’s try finding the molar mass of H2O
1.
Elements in the compound
2.
Atomic Mass
3.
How many of each element in the compound?
4.
Multiply
5.
Add
Example
S What is the molar mass of NaCl
1.
Elements in the compound
2.
Atomic Mass
3.
How many of each element in the compound?
4.
Multiply
5.
Add
Example
S What is the molar mass of Mg3(PO4)2
1.
Elements in the compound
2.
Atomic Mass
3.
How many of each element in the compound?
4.
Multiply
5.
Add
Let’s Practice!
Exit Ticket
S What is the molar mass of H2SO4?
S Write your answer on a half sheet of paper with your name
on it and hand it to me in order to leave!